Design of cold‐formed steel‐lightweight concrete composite beam

Abstract

Recent investigations by the authors, combining experimental testing and detailed numerical simulations, have demonstrated the feasibility and effectiveness of composite action in structural systems composed of built‐up cold‐formed steel (CFS) beams and lightweight concrete (LWC) slabs. The results show that these systems provide significant improvements in structural performance, particularly in load‐carrying capacity and stiffness. Existing design provisions for steel–concrete composite beams have largely been developed for hot‐rolled steel sections connected to normal‐weight concrete slabs using welded shear studs. In contrast, the CFS–LWC composite beams examined in this study utilise headed bolts as shear connectors. A key characteristic of these systems is that the ratio of bolt diameter to CFS top flange thickness commonly exceeds the maximum limit of 2.5 specified in EN 1994‐1‐1, placing them outside the direct applicability of current design rules. To address this gap, the study proposes a new strength prediction method specifically developed for built‐up CFS–LWC composite beams. The proposed approach was validated through extensive finite element analyses and parametric studies, demonstrating accurate and consistent predictions of flexural strength. The results provide a reliable design framework compatible with EN 1994‐1‐1 and AISC 360, offering practical guidance for the safe and efficient design of these emerging composite systems.